The present invention relates to model locomotives or railway engines and, more particularly, to scale model steam locomotives.
Steam locomotives, which are reproduced as models, were often fitted with a so-called equalized or compensated suspension system, the purpose of which was to enable the locomotive to travel uneven track whilst maintaining an approximately equal weight on each wheel mounted by the suspension system. Such an equalized or compensated suspension system is illustrated in FIG. 1 of the accompanying drawings. Referring to FIG. 1, the driving wheels 1 of the locomotive, which for clarity are only illustrated in broken outline, are driven by a steam cylinder 2 mounted at the front of the locomotive chassis 3 and connected to the wheels 1 by driving rods 4 in any conventional manner. Each driving wheel is fixed to an axle 5 which is journalled adjacent the wheel in an axle bush 6 slidably mounted on bearing surfaces provided on the adjacent main longitudinal chassis member 7 so as to be able to reciprocate vertically. The top of each bush is contacted by a pillar 8 which is vertically slidable in a holder 9 and has its upper end in contact with the middle of the bottom of a leaf spring 10 spanning the axle. This leaf spring is connected at its opposite ends to vertical links 11 which are, themselves, connected to the ends of compensating levers 12 rockably on appropriate pivots on brackets 13 fixed to the chassis member 7. The opposite ends of the compensating levers are connected by further vertical links to adjacent leaf springs, and so on.
It can be seen that this system of springs, levers and links enables a driving wheel to move in a vertical plane whilst to some extent sharing the alteration in spring pressure caused thereby with the leaf springs associated with adjacent driving wheels. This causes an alteration in pressure on these adjacent wheels. Furthermore, it will be apparent that this alteration affects the next sets of wheels, if any.
FIG. 1 also illustrates some modifications of the basic suspension system. Hence, at the front of the chassis, link 14 is not pivoted at the central point and this modification allows for equalisation or compensation due to an equal weight distribution along the length of the locomotive. At the rear of the chassis, a modification is shown in which the position of the leaf spring 10 and lever 12 are reversed compared with the basic system described above. Coil springs have also been used instead of or as well as leaf springs.
In the case of a model locomotive, it is feasible to reproduce exactly the details of a compensated suspension system in scales down to approximately one twentieth of full size. Some attempt has also been made to reproduce a compensated suspension system, as described above, in a scale locomotive of one forty-eighth full size but, in this model, the leaf springs were made as small castings so that, although an equalizing action was obtained, there was no spring or "give" in the suspension system.
In scale model locomotives down to approximately one eighty-seventh full size, it has been standard practice to provide for independent axle springing by means of small fixed coil springs bearing on the axle bushes. For increased realism of the suspension system, fixed dummy or immitation leaf springs and, sometimes also, dummy associated compensating levers, have been fitted. Such a construction provides a spring suspension system without equalization.
In some models, it is also known to provide a spring suspension system with partial equalization by using an arrangement of wires firmly fixed to appropriate points on the chassis and bearing on some or all the axle bushes. Such a system, however, does not produce an appearance representative of the original.